The present invention generally relates to food products and to methods for their preparation, and more particularly to the use of phytoglycogen as an additive or processing aid for foods, such as to provide an extended bowl life for ready-to-eat cereals when phytoglycogen coatings are applied to the food surfaces and to maintain crispness of fried foods after frying.
This invention was made with Government support under Grant No. 94-37500-0554, awarded by the U.S. Department of Agriculture. The Government has certain rights in this invention.
Phytoglycogen is a polysaccharide that constitutes a reserve for plants. It is the main component extracted in the water soluble, polysaccharide fraction in sweet corn and consists of glucose molecules linked by xcex1-D-(1xe2x86x924) bonds with xcex1-D-(1xe2x86x926) branch points. Shannon and Garwood, Genetics and Physiology of Starch Development, (2d edition, 1984). The accumulation of water soluble polysaccharide gives a creamy texture to prepared sweet corn products Maize endosperm mutants can be identified by their polysaccharide structure and content (amylose, amylopectin, and phytoglycogen) with up to 30 wt. % phytoglycogen of kernel dry weight found in some sugary corn mutant kernels. xe2x80x9cMaize Mutants. Part 1. Studies on Their Starch Components,xe2x80x9d Curxc3xa1 et al., Starke, 47(6), pp. 210-213 (1995); xe2x80x9cCereal Grains: A Study of Their xcex1-1,4-xcex11,6 Glycopolysaccharide Composition,xe2x80x9d Curxc3xa1 et al., Starke, 42(5), pp. 171-175 (1990).
Ready-to-eat (xe2x80x9cR-T-Exe2x80x9d) cereals are popular food items as breakfast foods and as snack foods. They are increasingly functioning as important nutritional supplements in American""s diets (according to a recent report published in Health News, a newsletter from the publishers of the New England Journal of Medicine). Most R-T-E cereals may be grouped into puffed or unpuffed cereal categories.
Generally, expanded or puffed cereals have little or no added fat, are not chemically leavened, and have a low density. They are very porous due to the cell structure formed by flashing off moisture at the extruder die. The porous characteristics of puffed cereals result in a cereal that can quickly become soggy in milk. U.S. Pat. No. 5,093,146, issued Mar. 3, 1992, inventors Calandro et al. (assignee Nabisco Brands, Inc.) discusses methods of extending cereal bowl life, such as by providing a heavy sugar coating. This patent describes using a mixture of pregelatanized waxy starch or modified waxy starch and at least one cold water swelling granule starch for coating a cookie dough intended for preparing a crispy, R-T-E cereal.
Unpuffed cereal types include flake, shreds, biscuits, shredded biscuits, and granola cereals. The preparations of these unpuffed cereal types typically include a toasting operation, as is described by U.S. Pat. No. 5,709,902, issued Jan. 20, 1998, inventors Bartolomei et al. (assignee General Mills, Inc.). This patent describes use of a high moisture sugar slurry for application to cereal flakes to provide a R-T-E cereal that exhibits greater crispness and extended bowl life.
Although it is known that sugar coated R-T-E cereals have generally longer bowl lives than regular R-T-E cereals, a heavy sugar coating on cereal is not necessarily desirable, particularly if the consumer does not wish to ingest substantial amounts of sugar with her cereal. However, the rheology of finished cereals is quite important for consumer acceptance. In general, the textural quality of an R-T-E cereal is greatly influenced, as judged by consumers and manufacturers, on initial crispness and ability to retain that crispness after immersion into milk.
Therefore, new methods for improving texture characteristics of food stuffs, particularly a characteristic such as cereal bowl life, remain desirable.
Meanwhile, plant breeding efforts have led to corn varieties with increased sweetness. The components of these corns have been objects of careful study, particularly since the rapid conversion of sugars to phytoglycogen after harvest and the resultant loss of sweetness is a major problem affecting quality. For example, the components of the sugary-1 (SU1) mutation in rice and corn have been examined. For rice, phytoglycogen was found to be present in the endosperm of all the mutants instead of starch. xe2x80x9cCorrelation Between Activities of Starch Debranching Enzyme and xcex1-Polyglucan Structure in Endosperms of Sugary-1 Mutants of Rice,xe2x80x9d Nakamura et al., Plant Journal, 12(1), pp. 143-153 (1997); For the corn mutants, there was found to be an increased sucrose concentration, a decreased concentration of starch (amylopectin) and an accumulation of the highly branched gluco-polysaccharide phytoglycogen. xe2x80x9cCharacterization of the Maize Gene Sugary-1, a Determinant of Starch Composition in Kernel,xe2x80x9d James et al., Plant Cell, 7(4), pp. 417-429 (1995).
To date, since consumers seem to prefer increased corn sweetness, and the rapid conversion of sugars to phytoglycogen after harvest results in loss of sweetness, increases in phytoglycogen in cereal based products such as those from corn would seem to be desirably avoided.
We have surprisingly discovered that phytoglycogen is a useful processing aid, or additive, for food products, such as by applying onto food surfaces, or by admixing phytoglycogen with foods that will be further processed. Phytoglycogen as a processing aid provides several advantageous properties to the foods: when applied as a coating on a food prior to frying, the fried food retains its crispiness for significantly longer than control samples; when a coating of phytoglycogen is applied to surfaces of many R-T-E cereals followed by drying, the so-coated cereal retains a crispy texture for an extended time when kept submerged in milk.
Accordingly, in one aspect of the present invention, a method of preparing a R-T-E cereal having an extended bowl life, comprises applying phytoglycogen to surfaces of the R-T-E cereal.
In another aspect of the present invention a food comprises a processing aid incorporated onto or in the food. The processing aid includes phytoglycogen. If the food to which the processing aid naturally includes phytoglycogen, then the phytoglycogen that is added in accordance with the invention increases the total amount of phytoglycogen, wherein the amount of phytoglycogen added is effective to increase resistance to wetting by a liquid with which the food is expected to be exposed.
Other aspects and advantages of the present invention will become apparent upon reading the specification and claims.